In the past, various anechoic test chamber constructions have been proposed for producing an essentially echo-free environment. Anechoic members, which are generally formed of solid, wedge-shaped blocks of sound-absorbing material, have long been used in such chambers. As conventionally employed, the larger base portions of the members are mounted adjacent the chamber wall, ceiling and/or floor surfaces; while their relatively small apex portions face the source of sound to be absorbed. In this conventional orientation of the members, they may be and usually are of considerable size. The length of the members, which is normally within the range of one-to-four feet, is approximately a linear function of the lower limiting frequency (i.e., the "cut-off" frequency) desired in each particular installation. In order to achieve a 1-octave reduction of the cut-off frequency with the use of conventionally-oriented anechoic members, their lengths must be approximately doubled. In addition to being expensive from the materials and fabrication viewpoints, large anechoic members of this type occupy much of the interior space of the anechoic chamber in which they are installed. The chamber design customarily requires a choice between the expense of constructing and maintaining a chamber of sufficiently large size to accommodate longer wedge-shaped members, versus the acceptance of a smaller chamber and a less satisfactory cut-off frequency. Additionally, conventionally-oriented anechoic members are difficult and expensive to maintain. When facing the source of wave energy to be absorbed, their more fragile apex portions are susceptible to damage from accidental impacts from persons or equipment within the chamber; and the crevices defined by an array of them tend to collect dust and the like which cannot be removed readily.